Origin of Theiler hepatitis was a century-old puzzle. For almost 100 years, veterinarians have puzzled over the cause of Theiler disease, a mysterious type of equine hepatitis that is linked to blood products and causes liver failure in up to 90% of afflicted animals. A team of US scientists has now discovered that the disease is caused by a virus that shares just 35% of its amino acid sequences with its closest-known relative. The team named it Theiler disease-associated virus (TDAV), and published the discovery in the Proceedings of the National Academy of Sciences1. Led by Amy Kistler at the...